Railway traffic controlling



Feb. 11, 1947. c. B. SHIELDS RAILWAY TRAFFIC CONTROLLING APPARATUS 5 Sheets-Sheet 1 Original Filed March 19, 1941 Easfbound B 3 RES 2m p .11 21% 1781211 01190 by{ 77 U GTE 0P ofhep N manual confm 201M EFS Fig; la 3 HIS MTORNE'Y Feb. 11, 1947. c. B. SHIELDS RAILWAY TRAFFIC CONTROLLING APPARATUS Original Filed March 19, 1941 5 Sheets-Sheet 2 lNV ENTOR gzzaplo Shields HIS A'TTORNEY Feb. 11, 1947. c, B. SHIELDS Re; 22,841

RAILWAY TRAFFIC CONTROLLING APPARATUS Original Filqd March 19, 1941 5 Sheets-Sheet 3 INVENTOR $11201 5. Shields HIS N r'roRNEY Feb. 11, 1947. c, SHIELDS Re. 22,841

RAILWAY TRAFFIC CONTROLLING APPARATUS 7 Original Filed March 19, 1941 5 Sheets-Sheet 4' INVENTOR Chan]? Shields HIS AZI'TORNEY 1947- c. E. SHIELDS Re; 22,341

RAILWAY TRAFFIC CONTROLLING APPARATUS Original Filed Msmch 19, 1941 5 Sheets-Sheet 5 SVNR SVRR 8H 1 P3 18 Q5 2 8Jr 00mm:

SVNR WES F019 3714 8B 4B 5? 8!) Signal 8714 8D 5 T mmzz d by N 5g E am 01 othep 8D 80PM W5 manual eontpol SVNRK 8V9}? Fig 19.

INVENTOR 11011122: B. Shields 15" ATTORNEY Reissued Feb. 11, 1947 22,841 RAILWAY TRAFFIC CONTROLLING APPARATUS Charles B. Shields, Penn Township, Allegheny County, Pa, assignor to lhe Union Switch and Signai Company, Swissvale, Pa., a corporation of Pennsylvania Original No. 2,349,680, dated May No. 334,196, March 19, 1941.

23, 1944, Serial Application i'or reissue May 18, 1945, Serial No. 5943M 1 14 Claims.

My invention relates to railway traffic controlling apparatus of the type in which coded track circuits are applied to single track, two direction signaling. More specifically, my invention relates to a signaling system or the above character in which the direction of trailic is established by a code sent out from a centralized traffic control location or by other suitable manual control. Accordingly, the directional control in the system embodying my invention is not automatic as in the case of standard A. P. B. circuits.

A feature of my invention is the provision for reversal of traffic direction without the use of the usual control line wires, by means of a momentary reversal of the track circuit polarity. Another feature of my invention is the provision of directional locking between head-block signals so that when either headblock signal is cleared or the section is occupied by a train the trafiic direction cannot be reversed 01' the opposing headolock signal cleared. A further feature of my inver. ion is the approach control of the wayside signals and the train control energy by means of polarity selection of the approach code.

One object of my invention is to dispense with all control line wires except the C. T. C. line and provide a safe and efiective system of two direction, single track signaling. A further object of my invention is to economize electrical energy in the system by providing for approach control of the Wayside and cab signals. A still further object of my invention is to make use of the same track battery which supplies the approach code for supplying the reverse track energy upon a reversal of trallic direction. Other objects, purposes, and features of my invention will be apparent from the description which follows.

I accomplish the foregoing objects by employing a momentary reversal of the track circuit polarity which causes an automatic cascading action over the track circuits of the section and which reverses the entering and leaving ends of each track circuit and of the stretch. Instrumental in providing this reversal is a second track relay in series with the main track relay, responsive only to the reverse track circuitenergy which is supp-lied momentarily to establish the new trallic direction. The approach energize.- tion of wayside and cab signals is accomplished through the medium of an approach code which is effective during the intervals between pulses of the ordinary signal control code. When the established trafilc is eastbound, the westbound signals will normally stop indication to a train moving westbound. A

be dark, but will display a similar operation takes place when the estabiished traific is westbound. I accompnsn on-ectlonal locking between neadblocxs by pfUVlCLlllg an approach or VR relay ror eacn traclc circuit,

' so controlled that clearing or a heaooiccs signal or entry of a train drops the nrst VN relay,

whereupon the act1on is cascaded to the end oi the stretch for governing the tranlc direction control relay at that end to insure the stop indication of the opposing headblock signal.

I shall describe one term of apparatus embodying my invention, and shall then point out the novel features thereof in claims.

Figs. 1a to 16, inclusive, of. the accompanying drawings when placed end to end with Fig. la at the left, are a diagrammatic view showing one form of apparatus embodying my invention.

Similar reference characters refer to similar parts in each of the several drawings.

Referring to the drawings, there is shown a stretch of single track railway having a passing siding at each end thereof. This stretch of track is divided by means of the usual insulated joints at locations I, 2, 4, 6A, 6, 8, and Ill into track circuit sections 2T, lI, EAT, GBT, 8'1 and MT, respectively. Locations l, 2, 4, ll, 8, and H] are signal locations whereas 6A is a cut section location which I have introduced to show the apparatus necessary in the case of a block whicn is very long. I shall use coded direct current or normal relative polarity supplied from a suitable battery El for the track circuit control, reversing the polarity of this current momentarily when the direction of traffic in the single track stretch is being reversed. Two rates of coding, 180 and per minute, respectively, are supplied by the constantly operating code transmitters iilfiCI and 15CT, only two codes being required for the three-position signaling system illustrated. Since alternating current is ordinarily required for operating the locomotive cab signal equipment, I have provided approach energized tuned alternators TA at the various locations for supplying the coded train control energy. For approach control, I make use of a feed back or approach code supplied from a suitable track battery E2, the impulses of which are effective during the ofi" intervals of the ordinary track circuit code, as will be described hereinafter.

At the left-hand or eastbound end of the stretch, I have provided an eastbound traffic control relay EFS which may be controlled by a remote operator over a C. T. C. line, or locally by means of a. manual lover or other suitable means. A corresponding westbound trafilc control relay WFS is shown at the right-hand or westbound end of the stretch. When relay EFS is energized, it initiates a cycle of operation which conditions the stretch (if unoccupied and the opposing headblock signal is at stop) for the passage of a train in the eastbound direction. Similarly, energization of relay WFS prepares the stretch for passage of a westbound train.

As shown in the drawings, the headblocksignals ZR and BL are at stop. This is also true of the remaining signals except 4R and 6R which are at clear since the last move through the stretch is assumed to have been in the eastbound direction. All of the signals are dark, however, since it is assumed that no train is approaching. Code is, however, being supplied to the track circuits since these are of the normally energized type. At each track circuit junction is a doublewound intermediate polarized direction selecting relay D which interchanges the entering and leaving ends of the associated track circuits and thereby determines the authorized traffic direction in these track circuits. At each end is a double-wound traffic direction selector (2D and 8D) which initiates the reversal of traffic direction and which controls all of the intermediate direction selecting relays as well as the trafiic direction selector at the other end of the stretch.

Looking at Fig. 1a, the direction selector 2D at that location has an energizing circuit for its left-hand winding which includes one terminal B of a source of current, front contact ll of relay EFS, front contact [2 of relay ZVNR (to be described later), and the other terminal C of the source. Relay 2VNR is now deenergized because relay ZZVN- is not operating, since front contact IQ of ZDRM is open. Accordingly, contact I2 is open, but selector relay 2D continues to occupy its normal position because its design is such that it continues to remain in its last operated position until a reversing impulse is received, whereupon it remains in the reverse position until again restored to normal. That is to say, the D relays are of the polar stick type. As shown, selector relay 2D occupies its normal position in which its contact 53 is swung to the left or N position. The closing of contact M of relay 2D prepares an energizing circuit for the right-hand winding of relay 2D so that if relay 2RTR should pick up (resulting from traffic reversal from eastbound to westbound) then selector relay 2D would be reversed by the momentary impulse of current which it would receive over front contact I of relay ERTR and its own contact M. The latter contact will immediately open, but not until a reversal of 2D has occurred and contact I3 is closed in its righthand or R position.

The impulse relay 21R. is well known in approach control circuits for coded wayside signaling. As used herein, this relay when deenergized connects the main track relay ZTR and the reverse track relay ZRTR in series across the track over the back point of its contact l6, and when energized, connects the battery E2 which supplies the approach code, across the track. It should be particularly noted that the code following track relays 2TR and ZRTR are oppositely poled so that but one of these relays (2TB) will normally follow code. When the track current polarity is momentarily reversed, however, relay ZRTR will be picked up as one step in the traffic direction changeover.

Relay ZTR controls the usual decoding transformer 2DT over its periodically operating contact l1 and so energizes the proceed relay N 4 over the resonant decoding unit IBDDU. Relay 2J will be picked up on 180 code but not on 75 code, in the usual manner. The caution relay 2H is likewise energized from a winding of the decoding transformer 2DT over the rectifying contact l8 of relay 2TB and this relay will be energized whenever ETR is following either 180 or 75 code, but will be deenergized when ZTR ceases to follow code. The impulse relay 21R is also energized from the decoding transformer 2DT by means of the winding I9 and the intermediate transformer 28. This transformer is not essential. but may be used to improve the timing characteristics of relay 21R. The impulse relay is of the biased polar type (biased to its deenergized position) and has a quick response whereby it is capable of following the impulses received from the decoding transformer. These impulses are, in effect, cycles of alternating current but the polarized feature permits the relay to pick up only on half-cycles of positive polarity, as indicated by the plus sign at one terminal of the relay, the bias insuring that the relay will release during each half-cycle of negative polarity. This manner of operating the impulse relay is well known and is shown and described in United States Reissue Patent No. 21,783 granted on April 29, 1941 to Herman G. Blosser for Approach control apparatus for railway signaling systems.

Relays ZVN and 2VR are polar code following relays which are instrumental in providing approach control and alsodirectional locking between the headblock signals. Since Fig. 1a is an end location, these relays become operative only when relay ZDRM is picked up following a reversal of relay EDR, that is, when front contacts [9 and 20 of relay ZDRM become closed and when the back point of contact 2| of the code transmitting relay ZCTM is also closed. Accordingly, the VN and VR- relays at the eastbound end will be operative only under westbound traffic conditions; the VN and VR relays at the westbound end being operative only under eastbound traflic conditions which is the direction illustrated in the drawings. At intermediate locations, however, the VN and VR relays will be operative whenever approach or feed back code is being received, that is, whenever all the track circuits in advance thereof to the opposing headblock signal are unoccupied. It will be noted that relays 2VN and ZVR are connected in series and are oppositely poled so that but one of these relays will operate at any given time, depending on the polarity of the feed back code received from the track. Relays ZVNR and ZVRR are merely slow acting repeaters of relays ZVN and respectively, and these remain constantly picked up provided that the respective control contact 22 or 23 is following code.

The tuned alternator 2TA is well known and is shown diagrammatically to simplify the disclosure. It is shown merely to make the disclosure more complete and its purpose is to provide a source of alternating cab signaling current in the absence of the usual alternating current transmission line. This tuned alternator is approach energized, as are the signals, and it delivers alternating current from its winding ZTAS to westbound traiTic in track circuit 4T, by virtue of the inclusion of winding ZTAS in series with the normal code current supply battery El in the feed circuit for track circuit 4T when relay ZDRM is energized and relay ZCTM is operating.

Having described some of the individual apparatus which enters into the operation of my system, I shall now proceed to describe the steps involved in a reversal of trafiic direction in the section and the operation which takes place as a train progresse through the section. As the apparatus stands, normal signal control code is being supplied to track circuit 3T from battery El by the coding action of relay SCTIx/i and this code is cascaded over the track circuits to the eastbound end in a manner to be described hereinafter. Relay 2TB follows code and operates re lay 21R which supplies feed back code from bat tery E2 to the track circuit 21, from which the feed back code is cascaded to the westbound end where it operates relay EVN, causing relay til/NR to be energized,

Since the drawings show the apparatus set up for an eastbound move, I shall assume that it is desired to reverse the traffic direction to permit a westbound train to pass over the stretch. To do this, the operator will send out a suitable C. T. C. code which will pick up the westbound stick relay WFS at the westbound end or the stretch shown in Fig. 1e. Since relay EBVNR is energized, the pickup of relay WFS will reverse traffic direc tion selector relay 8D to the right because the right-hand winding of this relay will now become energized over front contact 25 of WFS and front contact 25 of avian. Signal 81% being at stop, its home relay SRAl-l (the control of which is well known) will be deenergized so that back contact 26 will be closed. Just prior to the reversal of relay 8D, the code transmitting relay iiC'IM will be operating on 75 code by virtue of the 75 code circuit which extends from one terminal 13, con tact 21 of code transmitter "556T, back contact 26 of relay ERAH, and normal contact 23 of relay ElD, to the other terminal C. As will be shown hereinafter, the supply of '75 code to sec tion 8T causes 180 code to be supplied to section EBT and cascaded to the eastbound end from which a 180 feed back code is cascaded back to section 3T. Relay 8VN is now following these impulses of 180 feed back code and so causes its repeater 8VNR to remain energized due to code operation of front contact 28 of relay SVN. Re lay BVNR, when energized, checks that no train is occupying the section between signals 2L and ER, and also that the track circuit ET is unoc cupied and signal 2B is at SJGD so that its locking relay ARMS is energized.

As soon as relay 3D reverses, relay iiCTll/l ceases to follow code and relay BDRM is picked up over contact 30 of relay 813, now in its reverse position. The pick-up of ilDRM closes the front points of contacts Eli and so that an impulse of feed back energy can be received from section ST by relay 3TH. A feed back impulse will be transmitted to section ET even after normal code to this section is discontinued and relay released because the last release of 53TH will up the impulse relay 61R which will then transmit the feed back impulse from battery over the front point of contact Operation of relay BTR by this impulse of feed back energy causes response of impulse relay 81R whereupon a current impulse of reverse polarity is supplied from battery E2 to the tracl: circuit @T over the front contacts and it, an of relays HICDR and ELMS, respectively Relay IGCDR is merely a code detection relay for track circuit [ET and detects the unoccupied condition of this track circuit. The locking relay BLMS checks the stop indication of headblock signal 3L and is energized when and only when this signal is at stop.

The reverse current impulse transmitted over the front contact 15 of relay 81R from battery E2" is received by reverse track relay dRTR at location 6 and it will be noted that this relay is poled in such a direction as to be operated by an impulse of reverse polarity but not of normal polarity, the latter impulses operating relay GTR only. The pick-up circuit for relay ERTR may be traced from the upper track rail, wire 3f, back contact 38 of relay liDRM, wire 39, back point of contact id of relay EiIR, wire ll, relays 5TB and ESRTR, wire s2, bacl: contact is of relay EDRM, and Wire A l, back to the lower rail.

When relay QETR picks up, it closes the reverse energizing circuit for relay $513 over a path which includes front contact lit or SRTR, wire 35, normal contact ii of relay liD, wire 33, righthand winding of relay 5D, and front contact 39 of relay GVNR, The reversal of relay QED causes pick-up of relay GDRM over contact 53 of relay 1D in its reverse position, whereupon a holding circuit is established for relay 613 over front contacts 5i and 52 of relays tDRM and EDM, respectively. ihis holding circuit includes the lower winding of relay 61R and is sufficient to maintain this relay energized irrespective of whether the upper winding is or is not energized. Pick-up of SIR causes a reverse current impulse to be transmitted from battery E2 to the track circuit tiBT over a path which includes one terminal of the battery, wire 53, front point of contact 5d of eVNR, wire 55, front point of contact 55 of eDRlvi, wire 5?, upper rail of track circuit ESBT, lower rail, wire 53, front point of contact of EDRM, wires 62 and front point of contact 4d of MR, wire Si, and front point of contact E2 of EVNR, to the other terminal of battery E2.

At the cut section location EBA, the response of relay GARTH to the reverse code impulse and the consequent reversal of relay SAD and pick-up of relays iiADRM, EADM, and GAIR will be clear from the previous escription so that this description need not be repeated. Accordingly, it will be clear that a reverse code impulse will be transmitted into track circuit GAT and finally inc track circuit 6T, so that the action which was initiated through the pick-up of relay WFS at location Eiwhich resulted in the application of reverse current to the first westbound section has been cascaded over each intervening tract. circuit, in turn, until the first eastbound section lT has been reached. This cascading action ovides assurance that the stretch is unoccupied because otherwise, the reverse code could not pass beyond the occupied track circuit.

At location 2, relay ERTR will respond to the reverse code impulse and will reverse relay 233 over its front contact 55 and the normal contact M of relay 2D. When this happens, the control circuit for the eastbound head-block signal will be interrupted at normal contact 63 of relay 2D and a '75 code operating circuit will be established for relay ECTM over contact 54 of relay 2D in its :everse position the back point of contact 65 of lock relay ELAH for signal 2L. Since relay ZDRM is now picked up, normal polarity '25 code from battery E! is supplied to the track circuit lT over the front point of contact 2! of relay ZCTM. This code causes response of relay G'I'R at location 4 whereupon relay lH picks up and closes the code circuit for relay liCTM over the front point of contact E55, wire 61, 180 code contact 68, and Wire 69. The 180 code will be relayed into track circuit BAT by virtue of the operation of contact Ill of relay 4C'IM which codes the current from battery El. At location 6A, the front point of contact H of relay BATR will relay th 180 code into track circuit BBT in an obvious manner. The cascading of the normal code into track circuit 8T will be clear from the foregoing.

At location 8, since relay BDRM is picked up, relay 8TB will receive and follow the 180 code so that relays SJ and 8H will both be energized and westbound headblock signal 8L will be cleared over a circuit which includes front contact 12 of relay 8H, reverse contact 13 of relay 8D, and the front point of contact 75 of relay 3J. The clearing of this signal indicates that the stretch between headblock signals is unoccupied; that all of the D relays have been reversed and that the track circuits are in proper working order since code has been cascaded to the new entering end;

and that the opposing headblock signal is at stop. Since relay 8TB is now operating and relay SDRM is up, feed back or approach code for the approach energization of the signals will be supplied to section 8T over the front contact 75 of relay 81R and this code will be cascaded to the eastbound end since each of th intermediate TR relays is operating. The clearing of Signal 8L caused release of relay 8LMS so that the feed back energy supplied to the rails of section 8T is of the polarity effective to operate relay EVR but will not operate relay EVN. After a westbound train passes signal 8L and enters track circuit IfiT, the code detecting relay IBCDR will i be released so that after signal 8L goes to stop and relay SLMS picks up battery E2 will continue to supply approach code of the polarity effective to operate relay EVR. As relay BVN is released its contact l6 opens the circuit of relay GVNR and it is released to govern the po larity of the energy supplied from battery E2 at that location to the track circuit tBT. This approach code is thus cascaded over each intervening track circuit to track circuit 4T so that all of the VN relays are released and all of the relays VR are picked up. In this manner directional locking between headblock signals is obtained because the direction selecting relay D cannot be reversed, once a headblock signal has been cleared or a train enters the stretch, due to the fact that this relay is controlled over a front contact of the VNR relay which is a repeater of the relay VN, now deenergized.

Referring again to the entry of the train into the track circuit IGT, once the train passes location 8, the approach code received by relay GVB at location 6 will be shunted so that both relays FiVPt and EVRR will release, relay ESVNR having been previously released. This results in the energization of the tuned alternator ETA over the back contacts ii and E8 of relays 6 VRR and EVNR which results in the supply of train control current, coded at the proper rate by relay iiCTli/I, from the winding ETAS to the track rails of section 8T ahead of the train. Also, the proceed aspect of signal BL will now be displayed because of the closing of the clear signal circuit as follows: from one terminal +LB, back contact E9 of relay 6VNR, back contact of relay BVRR, wires 8!, 82, and 83, front point of contact 84 of relay SDRM, and front points of contacts 85 and 86 of relays 6H and BJ, respectively, to the proceed unit of the signal BL and terminal LB.

When the train enters the track circuit SET,

train control energy will be fed towards the train in a similar manner from the winding BATAS of the tuned alternator at location 6A. The clearing of signals 4L and 2L will occur in a similar manner to that described for signal 6L and so this description need not be repeated.

From the foregoing description, it will be apparent that I have provided an effective signaling system for two direction running on single track, with approach control and directional looking, all without the use of control line wires. Also, I have employed only the usual and 75 codes which provide three position signal aspects, but by transmitting these codes both in the normal and in the reverse direction under proper track circuit conditions and by making selective use of current polarity in these codes, I have provided a system in which the trafiic direction reversal and passage of traific in the new direction is readily and safely accomplished.

Although I have herein shown and described only one form of apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

i. In combination with a stretch of track over which trafiic may move in either direction, said stretch being divided into a plurality of track circuit sections, an eastbound and a westbound polarized traffic direction selector at the respective ends of said stretch, a polarized trafiic direction relay at the junction of each pair of said track circuit sections, an eastbound and a westbound headblock signal at the respective ends of said stretch, means governed by said westbound selector when occupying its normal position for supplying coded current of normal relative polarity to the end track circuit at the Westbound end and for maintaining said westbound signal at stop, means for cascading said coded current over the remaining track circuits of said stretch to the eastbound end, means efiective when said eastbound selector occupies its normal position and said coded current is eiTective in the section at said eastbound end for conditioning said eastbound signal to display its proceed indication, means at said eastbound end efiective for supplying feed back code impulses to said end track circuit during the off intervals of said coded current to maintain the adjacent trafiic direction relay in its normal position, means including said last-mentioned relay for cascading said feed back code over the remaining track circuits to said westbound end to maintain the remaining traflic direction relays in their normal position and provide approach energization for eastbound trafiic moving over said stretch, and means effective upon a reversal of said westbound selector from its normal to its reverse position for supplying an impulse of revers relative polarity to the section at said westbound end to reverse all of said tramc direction relays including said eastbound selector in sequence to thereby place said eastboundsignal at stop and condition said westbound signal to display its proceed indication.

2. In combination with a stretch of track over which trafiic may move in either direction, said stretch being divided into a plurality of track circuit sections, an eastbound and a westbound headblock signal at the respective ends of said stretch, a main and an auxiliary track relay for each of said sections receiving energy from the rails thereof and selectively responsive to current of normal and reverse polarity respectively, a traffic direction selector having a normal position for setting said westbound. signal at stop and for applying coded current of normal relative polarity to the westbound end section, said current being cascaded from the westbound to the eastbound end of said stretch by virtue of the response of the main track relays sequentially thereto, means controlled by the last main track relay for conditioning said eastbound signal to indicate proceed, means effective upon a reversal of said trafiic direction selector for supplying an impulse of current of reverse relative polarity to said westbound end section foroperating the auxiliary track relay associating therewith, said reverse polarity impulse being cascaded to the eastbound end or said stretch by virtue of the response of said auxiliary track relays sequentially thereto, the last auxiliary relay setting said eastbound signal at stop, and means controlled by last auxiliar relay for causing coded current to be cascaded from said eastbound to said westbound end for clearing said westbound headblock signal.

3. In combination with a stretch of track over which traflic may move in either direction, said stretch being divided into a plurality of track circuit sections, an eastbound and a westbound headbloclr signal at the respective ends of said stretch, a main and an auxiliary code following track relay for each of said sections connecting in series and normally receiving coded current from the associated section, said relays being selectively responsive to current of normal and reverse polarity respectively, an eastbound a westbound traffic direction selector at the respective ends of said stretch each having a normal and a reverse position for establishing eastbound and westbound direction respectively over said stretch, means controlled by said westbound selector when normal for placing said westbound headblock signal at stop and for supplying coded current of normal relative polarity to the track circuit at that end for operating the main track relay associated therewiti said main track relay causing coded current to be cascaded over the remaining track circuits by irtue the operation of the remaining main track relays, means controlled by the last main track relay and by said eastbound selector when normal for conditioning said eastbound headblock signal to indicate proceed, other means controlled by said last main track relay for cascading impulses of an approach code over the track circuits from the eastbound to the westbound end of said stretch during the oil intervals of said coded current, means efiective when said westbound selector is moved to its reverse position for transmitting a reverse polarity impulse to the trael: circuit at the westbound end for operating the auxiliary track relay associated therewith, said reverse polarity impulse being cascaded over the remaining sections by the intervening auxiliary relays to operate the last auxiliary track relay, and means controlled by said last auxiliary track relay for causing said eastbound selector to assume its reverse position and so to reverse the direction of traffic .over said stretch.

4. In combination with a stretch of track over which traflic may move in either direction, said stretch being divided into a plurality of track circuit sections, an eastbound and a westbound headblock signal at the respective ends of said stretch, a manually controlled selector having a normal position for eastbound traffic and a reverse position for westbound traffic, means con trolled by said selector when normal for placing said westbound headblock signal at stop and for supplying coded current of normal relative polarity to the westbound end track circuit, said current being cascaded over the track circuits to the eastbound end to thereby check the unoccupancy or said stretch, a normal code following track relay at the eastbound end selectively responsive to said coded current of normal polarity for conditioning said eastbound signal to indicate proceed, means effective when said manually controlled selector is reversed for supplying an impulse of current of reverse relative polarity to said westbound end track circuit, a reverse code following track relay for said last mentioned track circuit selectively responsive to said reverse polarity impulse, and means controlled by said reverse track relay for setting said eastbound signal to stop and for conditioning said westbound signal to indicate proceed to thereby reverse the direction of trafiic over said stretch. 5. In combination with a stretch of railway tract: over which traffic may move in either direction, said stretch being divided into a plurality of track circuit sections, an eastbound and a westbound heedblocls signal at the respective ends of said stretch, anv eastbound and a westcontrolled selector at the respective ends of d stretch each having a normal posi ion for eastbound traific and a reverse posit on for westbound traffic, a normal code followtracl: relay and a reverse code following track re ay for track circuit selectively responsive to current or normal and reverse polarity respectively, a polarized traific direction relay for each t a k circuit normally occupying its normal posi on. and caused to assume its reverse position in response to code following operation of its associated reverse track relay, means controlled by said westbound selector when normal for setting said westbound signal at stop and for supplying coded current of normal relative polarity to the westbound traelr circuit to thereby operate the normal track relay associated therewith and cause coded current to be cascaded over said sections to the eastbound end, means controlled by the last normal track relay and by saideastbound selector for conditioning said eastbound signal. to indicate proceed and for supplying current impulses to the sections of said stretch for approach control, said current impulses being supplied during the off intervals of said coded current, means eiiective when said westbound selector is reversed for supplying a reverse polarit impulse to the westbound end track circuit to operate the associated reverse track relay and so to reverse the polarized direction relay asso c1; ed therewith, means controlled by said lastinentioned relay and including the remaining reverse traclr relays for cascading said reverse impu se to the eastbound end, and means cont oiled by the last reverse track relay for reverssaid eastbound selector to thereby complete -e reversal of trailic direction over said stretch.

6. In combination with a stretch of track over which trafiic move in either direction, said st etch being divided into a plurality of track cir- Ci t sections, a manually controlled traflic threetion selector one end of said stretch, means controlled by said selector when normal for supplying coded current to the track circuit at that end of the stretch and cascading the coded current over the remaining track circuits to the other end to check unoccupancy of the stretch, means for supplyin impulses of normal polarity feed back code during the off intervals of said coded current to the end track circuit at said other end and cascading said feed back code over said stretch by means of a first code responsive relay associated with each section and selectively responsive to said normal polarity code, a second code responsive relay for each section arranged in energy receiving relation with the track and selectively responsive to feed back code of reverse relative polarity, means effective when a train enters said stretch at said one end and releases said first code responsive relay associated there- 'th for pole changing the feed back code sup- 1 d to the section in advance to thereby o erate said second code responsive relay for the next section and so to provide approach energisation, and means eil'ective upon a reversal of said traffic direction selector for momentarily reversing the polarity of said first-mentioned coded current to thereby operate traflic direction selecting apparatus for each section and so to reverse the traffic direction in said stretch.

7. In a two direction single track system of signaling, a track circuit at the entering end of the stretch for a given direction of traffic movement, including a two-position trafiio direction selector in its normal position for supplying coded current oi normal relative polarity to said track circuit at the entering end thereof, means for supplyin feed back code during the off intervals of said coded current to said track circuit at the leaving end thereof provided said single track stretch is unoccupied, a control relay energized in response to the presence of said feed back code, a polarized trafiic direction relay energized over a front contact of said control relay to there-by prevent reversal of said traflic direction relay during occupancy of said track circuit and so to provide directional locking, means effective upon a reversal of said trafiic direction selector for momentarily reversing the polarity of said Iirst-mentioned coded current, and a reverse track relay for said track circuit selectively responsive to said reverse polarity current for ZEvQiTSiIlg said polarized relay to thereby reverse the trafiic direction over said track circuit.

In a two direction single track system of signali g, a track circuit at the entering end of the h for a given direction of traffic movement, cans including a manually controlled two posiieon traflic direction selector in its normal position for supplying coded current of normal relative polarity to said track circuit for controlling traffic movement in said given direction over said track circuit, a polarized reverse track relay for st id track circuit, a polarized traific direction relay for said track circuit controlled over a front contact of said reverse track relay, means effective upon a reversal of said traffic direction selector for momentarily reversing the polarity of said coded current to thereby operate said reverse track relay and so to reverse said trafiic direction relay, and means controlled by said trafic direction relay for reversing the trafiic direction over said track circuit.

9. In a two direction single track system of signaling, a track circuit at the entering end of the stretch for a given direction of traffic movement, means including a two position traflic direction selector in its normal position for supplying coded current of normal relative polarity from direction has been reversed for supplying an appreach code from said second source to said track circuit.

19. In a two direction single track signaling system, a track circuit at the enterin end of the stretch for a given direction of trafiic movement, a two position trafiic direction selector, a code following relay, means including a normal contact of said selector for supplying code to said relay to cause code followin operation thereof, a polarized approach relay, means including a contact of said code following relay and effective when said selector is normal for alternately supplying coded current of normal relative polarity to said track circuit at the entering end thereof and connecting said approach relay to receive approach code impulses therefrom, said approach code impulses being supplied during off intervals in said coded current provided the stretch beyond said track circuit is unoccupied, a polarized normal track relay associated with said track circuit at the entering end thereof, a polarized reversed track relay associated with said track circuit at the leaving end thereof, means effective when said selector is reversed for connecting said normal track relay with said track circuit to cause operation thereof on an impulse of said approach code, means effective when said normal track relay is operated for supplying an impulse of reverse relative polarity to said track circuit to operate said reverse track relay, and a traific direction governing relay for said rack circuit controlled by said reverse track relay.

11. In a coded track circuitsignaling system, in combination, a stretch of track over which traffic may move in either direction, means manually controlled from a remote control ofilce for supplying coded energy to the rails of said track stretch at one end or the other in accordance with the direction of traffic being established, a signal at each end of the stretch governing entrance of trafiic into the stretch means for each signal manually controlled from said control office for conditioning the signal to clear dependent upon receipt of coded energy over the rails of the track stretch or for holding the signal at stop, and means for each end of the stretch for maintaining the supply of coded energy to the rails of the stretch as long as the signal at the other end of the stretch is cleared.

12. In a coded track circuit signaling system, in combination, a stretch of track over Which traffic may move in either direction, means manually controlled from a remote control ofiice for supplying coded energy to the rails of said track stretch at one end or the other in accordance with the direction of traific being established, a

13 stop, and means at each end of the track stretch governed over the rails of the stretch for maintaining the supply of coded energy to the rails of the stretch as long as the signal at the other end of the stretch is cleared.

13. In a coded track circuit signaling system, in combination, a stretch of track over which traffice may move in either direction, the rails of said track stretch being divided into a plurality of track sections, signals at the ends of said sections for governing movement of traffic into and through said stretch in one direction or the other, each of said signals being controlled by coded track circuit energy supplied over the rails of the associated track section towards the signal, means at each end of the stretch manually controlled from a remote control office for conditioning the signal governing entrance of traflic into the stretch at that end to clear dependent upon receipt of coded energy over the rails "of the associated track section or to hold said signal at stop, means at each end of the stretch manually controlled fromsaid remote control oflice for supplying coded energy to the rails of the track sec-' tion at that end of the stretch to thereby cause coded energy to be supplied in the same-direction over the rails of the remaining sections of the stretch, and means for each end of the stretch for maintaining the supply of coded energy to the rails of the section at that end of the stretch as long as the signal governing entrance of traffice into the stretch at the other end is cleared and also while said stretch is occupied by a, train.

14. In a coded track circuit signaling system,

in combination, a stretch of track over which trafllc may move in either direction, the rails of said track stretch being divided, into a plurality of track sections, signals at the ends of said sections forgoverning movement of trafiic into and through said stretch in one direction or the other, each of said signals being controlled by coded track circuit energy supplied over the rails of the associated track section towards the signal, means at each end of the stretch manually controlled from a remote control office for conditioning the signal governing entrance of trafiic into the stretch at that end to clear dependent upon receipt of coded energy over the rails of the associated track section or to hold said signal at stop, means at each end of the stretch manually controlled from said remote control office for supplying coded energy to the rails of the track section at that end of the stretch to thereby cause coded energy to be supplied in the same direction over the rails of the remaining sections of the stretch, and means at each end of the stretch governed over the rails of the stretch for maintaining the supply of coded energy to the rails of the section at that end of the stretch as long as the signal governing entrance of traflic into the stretch at the other end is cleared and also while said stretch is occupied by a train.

CHARLES B. SHIELDS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,357,518 Judge Sept. 5, 1944 2,357,240 Van Horn Aug. 29, 1944 

